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G. M. HOPKINS.

TELEPHONE TRANSMITTER.

No. 314,841. Patented Mar. 31, 1885.

. a I) L WITNESSES INVENTOR UNITED STATES PATENT OF ICE.

GEORGE M. HOPKINS, OF BROOKLYN, NEW YORK.

TELEPHONE-TRANSMITTER.

SPECIFICATION forming part of Letters Patent No. 314,841, dated March 31, 1885.

Application filed February 29, 1884.

To aZZ whom it may concern Be it known that I, GEORGE M. HOPKINS, a citizen of the United States, residing at Brooklyn, in the county of Kings and State of New York, have invented a new and useful Improvement in Telephone-Transmitters; and I do hereby declare that the following is a full, clear, and exact description thereof, reference being bad to the annexed drawings, forming a part of this specification.

7 My present invention is an improvement on the telephone-transmitter for whichLetters Patent were granted to me May 30, 1882, No. 258,757, the object being to render the action of the transmitter more efficient.

My invention consists in means for maintaining the electrodes in adjustment and for securing a more perfect electrical connection between the electrodes and the parts by which they are supported.

Figure l in the drawings is a diametrical section of the diaphragm-cell, showing the arrangement of the electrodes. Fig. 2 is a diametrical section of the electrodes, and Fig. 3 is a view of the contact-face of one of the electrodes.

Like letters of reference indicate similar parts in the different figures of the drawings.

The diaphragm-cell A is of the usual wellknown construction, and the diaphragmB contained thereby is connected in the mainline or local telephone circuit by the wire a in the usual way. The electrode 0, consisting in the present case of a carbon button provided with a metallic bushing, b, projecting beyond the carbon and toward the diaphragm, is secured to the diaphragm by ascrew, c, passing through the center of the diaphragm into a screwthreaded hole in the metallic bushing. The outer or contact face of the electrode O has several shallow radial grooves, 01, which readily admit air between the electrode 0 and the electrode D, which contacts with it. The electrode D, also of carbon, has a central metal plug,- e, in which is formed a smooth conical cavity for receiving the rounded end of the screw f, which supports the electrode D in light contact with the electrode 0, the screw 'f, passed through a metal plate, 9, supported by two or more fine metallic wires, 71., which pass through holes in the plate and are connected with tension-screws t, extending ra- (No model.)

| dially through the sides of the diaphragm-cell.

These screws z are each provided with a nut, j, by which the wires h may be put under any desired tension. The rounded end of the screw ftouches the wall of the conical cavity in the plug 6, and the electrode D by its own gravity is kept normally in very light contact with the electrode 0 by the sliding of the inclined surface of the interior of the plug 0 upon the rounded end of the screw f. The screw f, as

well as the plug 6, is made of non-oxidizable metal, and the current arrives at the electrode D through the wire a, wire h, plate 9, screw f, and plug 6. WVhatevcr changes take place in the current traversing the circuit in which my improved transmitter is included are pro duced between the contact surfaces of the electrodes 0 D when the diaphragm B is vibrated by the impact of sound-waves. The vibrations of the electrode D are limited by the distance of the screwf from the bottom of the conical cavity in thepluge and by the tension of the wires h. The distance between the end of the screwf and the bottom of the cavity in the plug 6 may be varied by turning the screw in one direction or the other, The wires it support the screw f, so that it is capable of yielding more or less under the movements of the electrode D. Either or both of the electrodes may be provided with radial grooves for admitting air to facilitate the action of the electrodes.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is

1. In a telephone-transmitter, a carbon elec trode having a metal center provided with a conical cavity, and an adj listing-screw held by a yielding support and provided with a rounded end touching the wall of the conical cavity in the metal center of the electrode, in combination with an electrode carried by the transmitterdiaphragm, as herein specified.

2. In a telephonetransmitter, the combination of the electrode D, the electrode-support ing device, consisting of the screw f, plate g, and two or more taut wires, l2, and the electrode O, substantially as herein specified.

GEORGE M. HOPKINS.

\Vitnesses:

Guns. L. Cor-1N, HERMAN C. HAGEN. 

